Tools for the rotation of screws, nuts and other threaded objects are often provided with a moment measuring or moment indicating appliance in order to guarantee that the tightening moment be within a prescribed range, since too low a moment does not give a tight joint and too high a moment damages the threaded object. Also for other tools intended for exerting a turning moment, there is a need for measuring or indicating the magnitude of the turning moment, e.g. when controlling the turning moment in springs, axles or bolts.
Basically, there exist two different types of tools. When using a moment measuring tool, the moment is determined as a deformation in some part of the tool, for instance in an elastic joint or in the shaft as such and the deformation can be read by an index on a scale or by digital electronics. However, the reading requires that the tool be moved slowly and that the scale be clearly visible, wherefore this type is unsuitable for routine installation work. Moment indicating tools merely indicate whether the moment is above or underneath an initially determined value, and is faster to work with when many screws are to be tightened with the same moment.
When using moment indicating tools, the difficulty resides in achieving an indication which is easily readable also under difficult conditions with noise and bad visibility. The invention foresees a tool with which the indication is effected in several simultaneous ways.